Everything check. Even a better CPU and more RAM. It just uses one core. And the GPU idles with SINZA 600% at about 10-13% each in radeontop. The fps then are at 5-10. Without the timeboost the fps and GPU-usage went up to playable framerates. Still the GPU could handle a lot more. Thinking back when I used fglrx that was indeed the fact. I had more fps and even with SINZA everything was smooth.
Drivers… :-(